French fried potato strips, commonly referred to as french fries, served in most fast food restaurants and other food service institutions, are purchased by the restaurant in bulk from commercial suppliers in the form of partially fried (par-fried) and frozen potato strips which are stored in frozen condition until shortly before serving. At that point the par-fried potato strips are prepared for consumption by finish frying in fat or oil.
Procedures for producing such par-fried potato strips are well known in the processed potato industry. Typically, raw potatoes are cut into strips of desired size and blanched in steam or hot water to inactivate enzymes and partially cook the potatoes. The blanched strips usually are then dehydrated to reduce their weight (as water) by up to 30% and par-fried for 30 to 90 seconds at about 300.degree.-400.degree. F. (149.degree.-204.degree. C.), and then frozen. In a preferred commercial procedure the blanched strips, prior to dehydration, are immersed in a dilute aqueous solution containing a food grade sequestering agent, such as sodium acid pyrophosphate (SAPP) and a reducing sugar, such as dextrose or glucose. SAPP, present at a level of about 0.5% to 1.5%, minimizes product discoloration by chelating metal ions such as iron and copper present in the processing water. Dextrose or other reducing sugar in the aqueous solution facilitates uniform color development upon frying.
The use of frozen par-fried potato strips has been widely adopted in fast food restaurants because of the convenience and savings in labor costs they provide. However, par-fried potato strips presently available suffer from the disadvantage that when finish fried for consumption the french fries lose their desired crispness after a relatively short period of time and become undesirably limp and soggy. Thus, while the french fries are crisp immediately upon removal from the fryer, they become limp and soggy within minutes after preparation due to the migration of internal moisture within the fried strips into the outer surface of the fries. Such limpness of the french fries results in objectionable appearance, taste and texture and is a principal feature by which consumers identify a poor product.
Also, fast food restaurant operators maintain proper serving temperature by holding the french fries under a heat lamp after finish frying. However, this tends to accelerate moisture migration, so that the french fries tend to even more rapidly become limp, chewy and soggy.
Suppliers of frozen par-fried potato strips have proposed a number of solutions in order to improve the crispness of french fries after finish frying. For example, the surface treatment of potato strips with firming agents such as calcium lactate, gums, alginates, high amylose starches, and other hydrocolloids has been suggested. However, these and other proposed solutions neither fulfilled initial expectations nor have been widely accepted in the industry as a satisfactory solution to the problem.
As an alternative to the use of frozen par-fried potato strips, some restaurants and other food service institutions prefer to serve french fries prepared from potato strips which have not been subject to an intermediate par-frying step. For example, the french fries may be prepared from potato strips which are cut from whole potatoes on the premises of the restaurant, with the freshly cut potato strips being washed and finish fried for consumption. Such french fries are perceived to have a more desirable, "homemade" flavor than french fries prepared from par-fried potato strips. However, french fries prepared from potato strips which are finish fried for consumption promptly after being cut, rapidly develop a limp and soggy texture after finish frying, particularly when held under a heat lamp. Despite any flavor preference which may be provided by french fries prepared from freshly cut potato strips, the rapid development of such objectionable texture characteristics is a significant disadvantage.